Sixty-six patients with non A, non B post transfusion hepatitis were followed from the onset of disease until their blood tests normalized, until death, or until the present time, unless they refused follow-up. Thirty patients had a spontaneous resolution of their biochemical disease. Four others had their serum transaminase return to normal only after immunosuppressive therapy. The remaining 32 patients still had abnormal transaminases at the time of their death (6) or when last seen (26). By actuarial analysis, only 54% of patients are predicted to develop a spontaneous biochemical remission after 3 years. No further spontaneous resolutions have occurred after that time. Initial and follow-up biopsies have revealed both chronic persistent and chronic active hepatitis. Two patients have shown histologic evidence of cirrhosis, and a third has developed a hepatic biochemical coagulopathy. However, no patient, to date, had developed overt evidence of hepatocellular failure or portal hypertension.